This invention relates to an improved process for hydroconverting carbonaceous materials to lower molecular weight products. More particularly, this invention relates to an improved catalytic process for hydroconverting carbonaceous materials to lower molecular weight products.
Heretofore, several catalytic processes for hydroconverting solid carbonaceous materials such as coal, lignite, peat and the like to lower molecular weight products and for converting heavier petroleum fractions such as atmospheric and vacuum residuals to lower molecular weight products have been proposed. The lower molecular weight products may be gaseous or liquid or a mixture of both. In general, the production of liquid products is particularly desirable since liquid products are more readily stored and transported and the lower molecular weight liquid products are conveniently used as motor fuels.
Heretofore, a large number of suitable catalysts have been identified as useful in such hydroconversion processes. For example, metal sulfides and oxides and mixtures thereof have been particularly useful as catalysts in such processes. Moreover, a host of catalyst precursors; that is, compounds that will either decompose or are readily converted to an active sulfide or oxide form have been identified. Such precursors include transition metal complexes such as transition metal napthenates, heteropolyacids and ammonium salts of various anions containing one or more transition metals. In general, the precursors used have either been soluble, to some extent, in the reaction medium itself or in a solvent which is added to the reaction medium. The solvents heretofore employed have been both organic and inorganic.
As is well known in the prior art, the effectiveness of the transition metal sulfide and oxide catalysts has been limited by their respective solubilities at atmospheric conditions or upon heating in the reaction medium itself or in the solvent used to incorporate the same into the reaction media. While the reason or reasons for this limitation on catalytic activity is not well known, it is believed to be due either to the particle size of the active catalyst species ultimately formed in the reaction media or as a result of poor distribution of the active catalyst species within the reaction mixture. Moreover, most, if not all, of the precursor species proposed heretofore require a treatment of some kind with a sulfur compound before the more active sulfide catalyst species is ultimately obtained.
Recently, and as described and claimed in co-pending U.S. patent application Ser. No. 608,308, filed on or about May 8, 1984, it has been proposed to use certain dihydrocarbyl substituted dithiocarbamates of certain metals and/or mixtures thereof as catalyst precursors to eliminate or at least reduce the impact of these effectiveness limitations encountered in the prior art catalytic hydroconversion processes. Moreover, and while certain dihydrocarbyl substituted dithiocarbamates have been found to be particularly effective as catalyst precursors in various hydroconversion processes, the search for even more effective precursors has continued. As a result of this continued search, certain precursors which are surprisingly more effective than the dihydrocarbyl substituted dithiocarbamates have been identified and the present invention relates to these surprisingly improved catalyst precursors and is drawn to an improved hydroconversion process wherein one or more of these surprisingly effective catalyst precursors is used.